Antenna system using parasitic elements and two driven elements at 90 deg. angle fed180 deg. out of phase



3,132,342 TWO DR HASE May 5, 1964 R. R. FORD ANTENNA SYSTEM USINGPARASITIC ELEMENTS AND IVEN ELEMENTS AT 90 ANGLE FED 180 OUT OF P 1962 2Sheets-Sheet 1 Filed July 12,

g LINEAR FEED l (HORIZONTAL DIPOLE) CIRCULAR FEED PRIOR ART R A R O R PINVENTOR ROLAND R. FORD May 5, 1964 R. R. FORD 3,13 4

ANTENNA SYSTEM USING PARASITIC ELEMENTS AND TWO DRIVEN ELEMENTS AT 90ANGLE FED 180 OUT OF PHASE Filed July 12, 1962 2 Sheets-Sheet 2 INVENTORROLAND R. FORD {Ma/Q4 ATTORNEYS -vi de an antenna system ferredembodiment of the ments, each of which is approximately one-quarterwave- I ANTENNA SYSTEM'USING'PARASITIC ELENENTS AND TWO DRIVEN ELEMENTSAT 90 ANGLE FED 180 OUT OF PHASE Roland R. Ford, District Heights, Md.,assignor to the United States of America as represented by theAdministrator of the National Aeronautics and Space Administration 7Filed July 12, 1962, Ser. No. 209,478 r I v 7 Claims. (Cl. 343-705)(Granted under Title 35, U.S. Code (1952), sec. 266) The inventiondescribed herein may be manufactured I and used by or for the Governmentof the United States of America :for governmental purposes without thepayment of any royalties thereon or therefor. .The present inventionrelates generally to improved antenna system with respect to the antennasystem of the ground'station. This problem arises because antennasgenerally have directional radiation characteristics and be cause theorientation of the satellite with respect to Earth is either unknown orcontinuously changing.

A partial solution to this problem has been theme of monopole antennaelements attached to the, outer surface of the satellite. FIG. 1 showsan antenna system which has been'used on previously launched satellites.It con; sists of four monopole .tached' ina common plane to the outersurface of the metallic satellite; The four monopole antenna elementsare. spaced 90 apart physically, and fed in phasequadratureelectrically. The radiation pattern of this antenna system hasfour lobes with appreciable nulls in-the plane :of the four monopoleantenna elements. In future satellite'applications, it is important thatthese nulls be reduced as much as possible. r

v The general purpose of the present invention is to profor general useand for use on satellites, which embraces all the advantages ofsimilarly employed antennas and which has lesser antenna pattern nullsthan previously used antenna systems. In aprefour monopole ele:

invention,

length of the transmitting frequency in physical length, are-insulatedlyattached to the outer surface of a metallic satellite. The four monopoleelements are located in a common plane and are spaced 90f apartphysically.- Two electrically. The remaining which are are fed 180 outof phase two monopole elements are parasitic elements I interconnectedto a load impedance for single frequency operation.

Dual frequency operation may be achieved by 1 ed S ates Pa n 10 f Itenna systems, and more particularly to antenna systems antenna elementsinsulatedly atadjacent monopole elements are active elements whichPatented May 5,1954

with a view to providing an optimum antenna system for the NASAAtmosphericStructure Satellite (8-6). The satellite is a pressurized35-inch sphere of stainless steel, which has a spinning motion in orbit;its tracking frequency is 136 mc. linearly polarized, and its telemetry'and command frequencies are respectively. .l36 and 120 mc.cross-linearly polarized. The antenna investigations were conducted on ascaled down model (6.5 inches in diameter, or about 125.3). of thesatellite, with a proportionately increased;frequency of 720 mc. I v 7An investigation was conducted on an antenna system mounted on ametallic satellite like the one shown in FIG. 1. The four quarterwavelength monopole elements were 'mounted on the equatorv (a'circumference) of the model. The four monopole elements were spaced 90?apart physically, and phased 90 apart electrically. Equatorial planepatterns were measured at 720 mc. for both linear feed (horizontaldipole) and circular feed. Linear feed and circular feed mean that themonopole elements are fed so thatthe electromagnetic waves emitted bythem are linearly polarized and circularly polarized, respectively.These patterns are shown in FIG. 2. The dashed line pattern was measuredwith linear feed. 'The maxi,- mum null depth. of, this pattern,comparedto the maxi mum pattern lobe, was 18v db. The solid linepatternwas measured with a circular feed source, and showed a'maximumnull depth of 14.5 db.. i v Another investigation was conducted on anantenna systern mounted on the model simulating a metallic satellite. Inthis investigation four quarter wavelength monopole elements weremounted on the equator of the model and spaced 90 apart physically.-'Two adjacent monopole elements were fed 180 out of phase. with a 720mc. source- The other ",two monopole elements were connected to a SO-ohmfloating load resistor. Equatorial planepatterns were measured for bothlinear and circular feeds. The maximum null depth for the linear feedwas 6 db and the maximum null depth for thecircular'feed was 6.3 db. vApolar plane pattern was measured for a circular feed and was found tohave only a 4 db null depth. This pattern was confirmed by recording ahori} zontal dipolepattern and a vertical dipole pattern. The vector sumof the horizontal and vertical components gave a pattern with less than3 db. nulls when compared to the antenna system.

replacing the load impedance with either a transmitter or receiveroperating at a second frequency. In this case,

a each fed or active pair of monopole elements will use the 'c elements.

other pair of monopole elements as parasi six monopole In anotherembodimentof the invention,

elements are insulatedly attached to the outer surface of i pair areadjacent to each other and are fed 180 out of phase. Ateach frequency,two monopole elements are fed, and the other four monopole elements areparasitic elements.

The invention is th A further object of the invention-is toprovide amultifrequency antenna system. f A still further objectof the inventionis to. improve the pmnidirectional coverage of an antenna system forsatellite application. i a I Other'objects and a fuller understanding ofthe inven: tion may be had by referring to the following description andclaims, taken in conjunction with the accompanying drawings, in which: ai j FIG. 1 shows a prior art antenna mounted on afnetallic satellite, inwhich oneembodiment of this invention incorporated; I j

FIG. 2 shows equatorial plane antenna patterns for a prior art antennasystem incorporated in the prior art an tenna shown in FIG. 1;

result of investigations performed FIG. 3 is a cross-sectionalview ofFIG 1 incorporating one embodiment of this invention; i j

FIG. 4 shows six monopole antenna elements insulatedly attached ot themetallic outer surface of a satellite in which another embodiment ofthis invention is incorporated; and

FIGS. a, 5 b, and 5c shows three mutually perpendicular cross-sectionalviews of FIG. 4 as indicated by section lines.5a-5a, 5b 5b, and 5c5c.

With reference to FIG..3 of the drawings, one embodiment of theinvention is illustrated as being incorporated in a metallic sphericalsatellite indicated generally by the physical length. Monopole antennaelements 11 and 14 are fed by transmitter 15 through a coaxial cable 16.

' The outer conductor of cable 16 is connected to the metallic shell ofsatellite 10 and the inner conductor of cable' 16 is connected toantenna elements 11 and 14. Transmitter 15 feeds cable 16 at a point onequarter .of a wavelength from antenna element 11 and three quarters of awavelength from antenna element 14. Consequently, the signals fed toantenna elements 11 and 14 are 180 out of phase. That is, if antennaelement 11 is fed at some phase angle 9 then antenna element 14 is fedat a phase angle of 0-180".

Antenna elements 12 and 13 are'connected to a floating resistor 17through a coaxial cable 18. The outer conductor of cable 18 isconnected. to the shell of satellite 10, and the inner conductor ofcable 18 is connected to antenna elements 12 and 13. Resistor 17isconnected to i of the plane containing monopole antenna elements 21,22, 23 and 24; FIG. 5b is a cross-sectional view of the plane containingmonopole antenna elements 22, 24, 25 and 26; and FIG. 50 is across-sectional view of the plane containing monopole antenna elements21, 23, 25 and 26. As illustrated in FIG. 5a, four monopole antennaele-' ments (21, 22, 23 and 24) are insulatedly attached, in the' sameplane 90 apart, to the outer surface of satellite 20. Monopole antennaelements 21 and 22 are fed by a transmitter 27 through a coaxial cable28. The outer conductor of cable 28 is connected to themetallic shell ofsatellite and the inner conductor of cable 28 is connected to antennaelements 21 and 22. The transmitter 27 feeds cable 28 at a point onequarter of a wavelength of the transmitter operating frequency fromantenna 22 and three quarters of a Wavelength'of this operatingfrequency from antenna 21. Antenna elements 21 and 22 each have aphysical length equal to one quarter of a v wavelength of the operatingfrequency of transmitter 27.

cable 18 at a point three'quarters of a wavelength from differences ofthe two distances be zero or some multiple of one half .of a wavelength.The floating resistor is connected to cable 18 to simulate equipment(transmitter or receiver) which might be connected to the antennaelements. The value of resistor 17 is not critical. In the operation ofthe embodiment of the invention 7 shown inFIG. 3, signals applied tocable 16 by transmitter 15 are applied to antenna elements 11 and 14..Because of the relative lengths of cable 16 fromtransmitter 15 toantenna elements 11 and 14, the signals applied to antenna elements 11and 14 are 180 out of phase. Antenna elements 12 and 13 are parasiticand improve the omnidirectional coverage of antenna elements 11 and 14.It should be noted that dual frequency operation may berealized by 'theembodiment of this invention shown by FIG. 3, if the resistor 17 isreplaced by a transmitter or receiver operating at a second frequency.If this be true, each pair of monopole elements will be fed or active atone frequency and will be parasitic at the other fre-. quency. For thisdual frequency operation monopole elements '12 and 13 should be onequarter of a Wavelength of the second frequency, in length, and monopoleelements 11 and 14 should be one quarter-of a wavelength of theoperating frequency of transmitter 15, in length.

With reference to FIGS. 4 and 5 of the drawings, another embodiment ofthe invention is illustrated wherein the spherical satellite isindicated generally by the 'refer ence character 20. FIG. 4 shows themetallic spherical to the surface of the satellite and electricallyinsulated from the satellite with asuitable insulating material. FIG. 5shows'three mutuallyperpendicular cross-sectional views of FIG. 4; FIG.5a is a cross-sectional view transmitter 31 through a coaxial cable Asillustrated in FIG. 5b, four monopole antenna elements. (24, 25, 22 and26) are insulatedly attached,'in the same plane apart, to the outersurface of satellite 20. Monopole antennaQelements 24 and 25 are fed byatransmitter 29 through a coaxial cable 39. The outer'conductor of cable'39 is connected to the metallic shell of the satellite 20, and theinner conductor of cable 30 is connected to antenna elements 24 and 25.The transmitter 29 feeds cable 30 at a of the transmitter operatingfrequency from antenna element 25 and three 'quarters of a wavelength ofthis frequency from antenna element 24. i Antenna elements 24 and 25each have a physical length equal to one quarter of a wavelength of theoperating frequency of transmitter'29. i

As illustrated in FIG. 50, four monopole antenna elements (21, 25, 23,and 26) are insulatedly attached, in the same plane 90 apart, to theouter surface of satellite 20. Monopole antenna elements 23 and 26 arefed by a 32. The outer conductor of cable 32 is connected to themetallic shell of satellite 20, and the inner conductor of cable '32 isconnected to antenna elements 23 and 26. The transmitter 31 feeds cable32 at a point one quarter of a wavelength 'of the transmitter operatingfrequency from antenna element 26, and three quarters of a wavelength ofthis frequency from antenna element 23. Antenna elements 23 and 26 eachhave a physical length equal to one quarter of'a wavelength of theoperating frequency of transmitter 31. a

In the operation or the embodiment of the invention shown in FIGS. 5a,5b, and 5c, signals applied to cables 28, 30 and 32 by transmitters 27,29 and 31 are respectively applied to antenna element pairs 21, 22; 24,25; and 23, 26. The antenna elements of each pair are fed out of phaseby their respective transmitters. Transmitter 27,'at its operatingfrequency, feeds antenna element pair 21, 22, and antenna element pairs24,25 and 23, 26 are, parasitic elements at that frequency. Transmitter29, at its operating frequency, feeds antenna element pair 24, 25 andantenna element pairs 21, 22 and 24, 25 are parasitic elements at thatfrequency. Transmitter 31, at its operating frequency, feeds antennaelement pair 23, 26, and antenna element pairs 21,22 and 24, 25 areparasitic elements at that frequency; I

The parasitic actions of the three antenna, element pairs are optimumwhen the three operating frequencies are fairly close to each' other,preferably within 20%,.

ment of FIG. 3; in addition, it can radiate at three independentfrequencies simultaneously. If necessary, tuned circuits can be used tokeep each pair of fed antenna elepoint one quarter of a wavelength unitsfeeding each pair of more uniformly Within the satellite.

Obviously numerous modifications or variations of the present inventionare possible in light of the above teachings. For example,

transmitter. It is therefore to be understood that within the scope ofthe appended claims the invention may be practiced otherwise than asspecifically described herein. What is claimed is: a 1. An antennasystem for use on an unoriented spherical metallic satellite comprising:four monopole antenna elements each having a physical length equal toone 7 quarter of a wavelength of the operating frequency of the antennasystem; means for insula'tedly attaching the said four monopole antennaelements to the outer surface of the satellite in a common plane 90apart; means for applying, at the operating frequency, signals to be.radiated 180 out of phase to anadjacent two of said four connected tothe other two of said four monopole antenna elements to form an antennaelement pair whereby the omnidirectional coverage of the antenna systemis improved; i V K y 12. A dual frequency antenna system for use on anunf oriented'spherical metallic satellite comprising: four monopoleantenna elements two of which have a physical length equal to onequarter of a wavelength of one of said dual frequencies and the othertwo of which have a the othenof said dual frequencies; means forinsulatedly attaching said four monopole antenna elements to the outersurface of the satellite in a common plane 90 vapart'with the monopole'antenna elementshaving equal lengths adjacent to each otherrmeans forapplying, at one of said dual frequencies, signals to be radiated 180out of phase to the two monopole antenna elements whose lengths areequal to one quarter of a wavelength of said one ofsaid dualfrequenciesyand means for applying, 'at the other of said dualfrequencies, signals to be radi- Iated .180 out of phase to the twomonopole antenna ele ment's whose lengths are equal to one quarter of awavea length of said other of said dual frequencies whereby two,

monopoleantenna elements are active and two are parasitic for each ofsaid dual frequencies.

1' 3. A multifrequency antenna system foruse on-an un- Yorientedspherical metallic satellite comprising; six monopole antenna elements,twoof which have a' physical fjquenc'y, two of which have a physicallength equal to one of which have a physical length equal to one quarterof a attaching said six'monopole antenna elements at points "equallyspaced around the outer surface of the satellite -with the monopoleantenna elements having equal lengths adjacent to eachother; frequency,signals to be radiated 180. out of phase to the 'tion where balancedweight is importantthe circuit antenna elements can be spaced areceivercan be substituted for any monopole a ntenna elements; and afloating resistor means physical length equal to one quarter of aWavelength of =length equal to one quarter of a wavelength of a firstfremeans for applying, at said'tirst to one quarter of a wavelength ofsaid first frequency; means for applying, at said be radiated 180 out ofanterma elements whose lengths are equal to one quarter of a wavelengthof said second frequency; and means for applying, at said thirdfrequency, signals to be radiated 180 to thetwo monopole antennaelements whose lengths are equalto one quarter of a wavelength of saidthird frequency whereby two monopole antenna elements are active andfour are parasitic for each of said first, second, and thirdfrequencies.

4. An antenna system for use on an unoriented satellite comprising:fourmonopole antenna elements equally spaced around and mounted theouter surface of the satellite; means for applying signals to beradiated 180 monopole antenna elements, whereby the other adjacent twomonopole antenna elements form a parasitic antenna element pair whichimproves the omnidirectional coverage of the antennasystem.

6. A multifrequency antenna system for'use on an unoriented satellitecomprising:

elements attached. at diiferent points to the outer surface of thesatellite; means for applying separate different frequency signals to beradiated elements of the six monopole antenna elements'whereby threedifferent frequencysignals are radiated simultan e-' ouslyeach signalbeingradiated by an active antenna element pair and" by two parasiticantenna elementpairs to improve the omnidirectional coverage of, theantenna 7. An antenna system for radiating signals at three diiferentfrequencies simultaneously, comprising: three pairs of monopole antennaelements formedby adjacent monopole antenna elements with the twoantenna elementsof each pair being approximately equal to one quarter:of a wavelengthof a second frequency, and two twol monopole antennaelements whose lengths are equal quarter of a wavelength of theiroperating frequency in length; means for applying different frequencysignals to each pair of antenna elements and for applying'the signals tothe two monopole antenna elements of each" I out of phase whereby eachsignal is radiated by an active antennaxelement pair and by twoparasitic antenna element pairs to improve the, omnidirectional,coverage of the antenna system. 1 a 3 wavelength of a third frequency;means for insulatedly References Cited in the file of this patent V v{UNITED STATES PATENTS 7 2,224,898 Carter m-. Dec..17,f1940 secondfrequency, signals to .0 phase to the two monopole in a common plane, onj p out of phase to an adjacent two of the four monopole antennaelements; and means six monopole antenna to each of three antennaelement pairs formed by adjacent monopole antenna

1. AN ANTENNA SYSTEM FOR USE ON AN UNORIENTED SPHERICAL METALLICSATELLITE COMPRISING: FOUR MONOPOLE ANTENNA ELEMENTS EACH HAVING APHYSICAL LENGTH EQUAL TO ONE QUARTER OF A WAVELENGTH OF THE OPERATINGFREQUENCY OF THE ANTENNA SYSTEM; MEANS FOR INSULATEDLY ATTACHING THESAID FOUR MONOPOLE ANTENNA ELEMENTS TO THE OUTER SURFACE OF THESATELLITE IN A COMMON PLANE 90* APART; MEANS FOR APPLYING, AT THEOPERATING FREQUENCY, SIGNALS TO BE RADIATED 180* OUT OF PHASE TO ANADJACENT TWO OF SAID FOUR MONOPOLE ANTENNA ELEMENTS; AND A FLOATINGRESISTOR MEANS CONNECTED TO THE OTHER TWO OF SAID FOUR MONOPOLE ANTENNAELEMENTS TO FORM AN ANTENNA ELEMENT PAIR WHEREBY THE OMNIDIRECTIONALCOVERAGE OF THE ANTENNA SYSTEM IS IMPROVED.